The APO3 is a black box designed to prevent a vehicle battery from being discharged and damaged by a DC load. Typically it is used to switch a radio transceiver off 10 minutes after the vehicle is shut off.

The APO3 is designed for 12 volt vehicle electrical systems with negative ground. It can switch up to 20 amps and carry up to 30 amps. The shutdown voltage can be set to one of four pre-programmed voltages (11.8, 12.1, 12.7, 13.05 volts) using two DIP switches; the shutdown delay can be set to one of four pre-programmed times (0, 5, 10, 20 minutes). The device is housed in a sturdy ABS plastic case.

The APO3 is basically a voltage controlled switch. When the vehicle voltage is higher than the APO3 set point, the relay is
turned on and power is provided to the load side. When the voltage drops below the APO3 voltage set point and stays there for
longer than the time set point, the APO3 relay turns off and power is removed from the load side.

The APO3 has a bright yellow LED to indicate its status and it has a slide switch that can be used to turn the load on regardless
of the input voltage.

Using the factory default settings, the APO3 will turn on the load when the vehicle voltage rises above 13.05 volts. This typically
occurs within a few seconds of starting the vehicle. The load remains powered as long as the engine is running. When the engine is shut
off, the vehicle voltage sinks below 13.05. The APO3 waits until the voltage has been less than 13.05 volts for 10 minutes and then turns
the load off.

The APO3 is ideal for use with mobile APRS / AVL stations. It allows the radio to transmit a few position reports after the
vehicle is shut off before turning off the radio and GPS. This reduces clutter on the APRS / AVL channel and prevents the vehicle
battery from discharging.

The APO3 is installed between the vehicle battery and the DC load. Typically, the load is a mobile radio transceiver and accessories.
Standard installation involves cutting the DC feed to the radio and using butt splice connectors to install the APO3. This usually
takes 10 minutes or less. If you use Anderson Power Pole connectors, we offer an APO3 with Power Poles already installed; this makes
installation a literal snap. If you want to change the factory set points, you will need to remove the cover and flip a couple of
small switches. Important: The APO3 is not suitable for installation within the engine compartment.

I've had my TM-D700 in my car for about 6 months, and I was always
forgetting to turn the rig on when I got in, or I'd forget to turn it
off when I got to wherever I was going. I'm an electrical engineer, and
I've built a variety of custom circuits, so I was thinking of designing
a circuit to control the power to the radio. But then I saw the
APRS World booth at the Dayton Hamvention, and realized that the APO3 did
everything I needed, and more. It has more features and is cheaper than
anything I could have designed and built myself. I like the fact that
it leaves the radio on for 10 minutes (or 3 other settings) after I shut
the car off, which allows my final position to get transmitted at least
once. And the override switch is handy for those times when I want to
use the rig when the engine is off. I was able to use the default
voltage setting, but I like that there are 3 other voltage settings just
in case. It installed in my car in about 5 minutes, and has been
working flawlessly for almost 2 months now. I just bought another D700
for my truck, and I'm getting another APO3 for it. In my opinion, the
APO3 is a very useful, high-quality product that any ham with a mobile
radio would find extremely helpful.